Vacuum packaging

ABSTRACT

A vacuum packaging system whereby upper and lower films are vacuum sealed about an article. The article to be packaged is placed on a lower film having upwardly extending projections. A vacuum is drawn about the edges of the film and an upper sealing film is positioned above the article and pulled tightly thereabout by the vacuum. The projections allow substantially complete evacuation of air from the enclosed article before the films become completely sealed together to form an airtight package.

United States Patent Johnson Oct. 7, 1975 VACUUM PACKAGING PrimaryExaminer-Travis S. McGehee I t H. W ll h V t If. [75] nven or I lam J0nson en ura Cal Attorney, Agent, or FirmKenneth J. Hovet [73] Assignee:Svenska Manufacturing Corporation, Santa Rosa, Calif.

Filed:

[5 7 ABSTRACT A vacuum packaging system whereby upper and lower filmsare vacuum sealed about an article. The article to be packaged is placedon a lower film having upwardly extending projections. A vacuum is drawnabout the edges of the film and an upper sealing film is positionedabove the article and pulled tightly thereabout by the vacuum. Theprojections allow substantially complete evacuation of air from theenclosed article before the films become completely sealed together toform an airtight package.

8 Claims, 16 Drawing Figures [22] Aug. 20, 1974 [21] Appl. No.: 499,051

[52] US. Cl. 53/112 A; 53/141 [51] Int. Cl. B65B 31/02 [58] Field ofSearch 53/22 A, 112 A, 141

[56] References Cited UNITED STATES PATENTS 3,449,886 6/1969 Connelly etal 53/22 A X 3,830,365 8/1974 Krueger et al. 53/22 A X US. Patent 00.7,1975 Sheet 1 of 4 3,910,008

US. atent Oct. 7,1975

Sheet 2 of 4 FIG.8

U.S. Patent Oct. 7,1975

Sheet 3 of 4 3,910,008

mmlw" I 8 U.S. Patent Oct. 7,1975 Sheet 4 of 4 3,910,008

VACUUM PACKAGING BACKGROUND OF THE INVENTION 1. Field of the InventionThe present invention relates to a packaging system and, moreparticularly, to the vacuum sealing of an article between packagingmaterials.

2. Description of the Prior Art Numerous techniques have evolved overthe years for packaging products between films, or against a cardboardbacking or within a pre-shaped container. For example, US. Pat. No.3,377,770 discloses a skin packaging apparatus whereby a porous base padis placed over a vacuum platen and a product is placed thereon. Plasticsheet material is heated and stretched tightly over the product bydrawing a vacuum through the porous base pad. This process requiresnumerous manual manipulations and is not suitable for high volumepackaging. Additionally, it is not suited for products which aredesirably maintained in an airtight condition inasmuch the porous basepad will allow air to pass back into the package.

US. Pat. No. 3,634,993 to Pasco et al. provides a technique for sealinga product between a pair of films by placing the product on a bottomfilm which is on a heated reciprocable platen. A vacuum is pulled aboutthe periphery of the platen while it is moved into seal ing engagementwith an upper chamber having an upper film stretched thereacross. whenthe films contact each other, the vacuum is released and air is injectedabove and below the films to push out any air lingering about theproduct. The two films become heat sealed together to form an airtightpackage.

The above sequence of steps is substantially similar to that shown inUS. Pat. No. 3,491,504 wherein movable platens and dome-like chambersoperate in conjunction with sequential vacuum and air injections to pulland push, respectively, the films tightly against a product.

An inherent disadvantage with the prior art systems is the fact thatwhen a vacuum is drawn from between upper and lower films, ambient airadjacent the edges of the films is removed first. As a result, the filmshave a tendency to become sealed together at their periphery before theinterior of the package can be evacuated of air. Residual air, ofcourse, can be highly deleterious to various types of food products. Tocompensate for this, packagers have used the aforementioned airinjections, or they have injected nitrogen into the package to displacethe harmful air or they have used preformed films to minimize theinterstitial space about the product. The air injection techniquerequires the films to be sealingly enclosed between a chamber and platenmeans so that the pressurized air will operate to push against the filmsand expel any air trapped about the product. Unquestionably, suchtechniques require an unnecessary number of process steps, they requirehigh capital costs in equipment, they are inefficient, time consuming,and are generally unsuitable for assembly line operation.

SUMMARY OF THE INVENTION In accordance with the present invention, an.improved packaging system is provided whereby a substantially completeexcavation of air from a package can be obtained with a simplifiedhighly efficient apparatus. This is accomplished by providing amultiplicity of projections extending toward the interior of a packageon at least one of the wrapping films.

In general, the invention contemplates the placement of a bottom film ona vacuum plate having vacuum ducts adjacent the film periphery. Anarticle is placed on the film and a transfer housing moves an upper filmover the article. Air is drawn through the vacuum ducts from theperiphery of the bottom film to remove air from about the article. Theevacuation of air continues during the downward movement of the upperfilm and after the upper and lower films contact each other. This ispossible because of the passageways formed between the inwardlyextending projections and the upper film. The removal of air continuesuntil substantially all air is removed from about the article and thefilms become tightly drawn against each other.

A permanent airtight package results when the portions of the films thatoverlap the periphery of the article become sealed to each other. Asuitable seal may be effected by heat, in which case the films comprisea heat sealable composition and the transfer housing and/or vacuum plateis provided with means for heating the films. Alternatively, a seal maybe effected by coating at least one of the films with an adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view ofapackaging apparatus constructed in accordance with the presentinvention;

FIG. 2 is a side elevation view of the apparatus of FIG. 1;

FIG. 3 is an end elevation view taken along the line 3-3 of FIG. 2;

FIG. 4 is an elevation sectional view taken along the line 44 of FIG. 2;

FIG. 5 is a perspective view partially broken-away of the upper sheettransportation assembly of the apparatus of FIG. 1;

FIG. 6 is an elevation sectional view taken along the line 6-6 of FIG.3;

FIG. 7 is an elevation sectional view taken along the line 77 of FIG. 3;a

FIG. 8 is an end elevation view taken along the line 8-8 of FIG. 2;

FIG. 9 is a side elevation view partially broken-away taken along line9-9 of FIG 8;

FIG. 10 is a broken-away perspective view taken along line 10-10 of FIG.9;

FIG. 11a is a vertical sectional view ofa modification of the vacuumplate of the apparatus of FIG. 1 showing vacuum duct shields operatingin conjunction with a bottom film;

FIG. 11!) is a top plan view of the vacuum plate of FIG. 11a without abottom film;

FIG. 12 is a modification of the bottom sheet-forming assembly shown inFIG. 1;

FIG. 13 is an enlarged scale broken-away partial sectional sideelevation view showing the apparatus of FIG. 1 in operation; I

FIG. 14 is a sectional view taken along line 14-14 of FIG. 13; and,

FIG. 15 is a plan view taken along line 15-15 of FIG. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,and, more particularly to FIG. 1 thereof, a perspective view of theoverall packaging apparatus is shown. This view includes an adjunctembossing assembly 12 for impressing projections onto a plain surfacedmaterial for use as a bottom wrapping film. The assembly is readilydetachable and may be operated as a separate unit for producing apackaging film in large quantities and stored in rolls for later use.

In general. the primary elements comprising the packaging apparatus ofthe present invention include support means shown generally as 90 and 94in FIG. 1, vacuum plate means 14, a movable housing 18, and a filmtransfer means 22. An upper sheet transportation assembly is a desirableelement of the invention, but its use is optional depending on how theapparatus is operated.

The support means preferably comprises two sections 90 and 94 located atopposite ends of the vacuum plate means 14. Both sections are elevatedto a position about level with the top surface of vacuum plate 14. Thefirst section 90 comprises a belt 130 mounted between end roller 132 andsecondary drive roller 134. An intermediate plate 133 is used to providesupport for the belt between the rollers 132,134, however, idler rollerscould be utilized equally as well. It is desirable to provide anunderlying support for the belt at this location since such area isconvenient for the placement of articles to be packaged. An article tobe packaged will preferably be placed on the bottom film 38 as it isdrawn in the direction shown by arrow A in FIG. 2. Of course, it isdesirable to rotate the belt 130 at the same speed the film is drawnthrough the apparatus.

The second support section 94 includes pressure roller 104 and amultiplicy of rollers 97a,b,c, mounted across the top of opposingsidewalls 13:1,!) of frame housing 15. The second section will bedescribed in detail hereinafter, however, it is to be understood that anendless belt conveyor, paddle or flight conveyor, chain mounted clampingmeans, hook means or the like would work equally well. It iscontemplated that this section will support the sealed package prior toits removal for packing or, in the case where the bottom film iscontinuous. its conveyance to the cutting station 112. As such, thespecific support means used will be dictated by the type of articlebeing packaged, its size, weight and structure.

Located between the first and second support sections is the vacuumsealing station shown generally as reference numeral 92. At thislocation an article is vacuum sealed between an upper and lower film.Such occurs when housing 18 moves a film over a product located on anembossed film situated between fluid pas sageways 32 on a vacuum plate14. In the preferred embodiment, the housing comprises a continuousconduit formed into an openwork such as the rectangularsh'aped housingframe 19 shown in FIGS. 1, 2, 4 and 14. The frame 19 has a bottom edge44 which is constructed to sealingly impinge an upper film against thevacuum plate radially outside the vacuum plate passageways 32.

Also included with the housing assembly 18 is heating means 80 and heatshield 21 (see FIG. 4), The heat shield surrounds the heating means andoperates to reflect and/or contain heat emanating from the heatingmeans. The heating means may comprise one or more banks of conduction,radiant and/or convection type heaters such as for example, hot airunits, infra-red lamps or electrical resistant units.

The housing assembly is connected for movement to reciprocation means24. This reciprocation means includes a pneumatic or hydraulic cylinderand piston arrangement which is secured to stationary frame plate 23which, in turn, is affixed to the basic apparatus frame structure shownas reference numeral 10. The reciprocation means 24 is located betweencross plates 27 which are secured to a movable overhead support frameshown generally as 26. The support frame reciprocates within the basicframe structure on roller devices 23. The roller devices are affixed tocross beams 31 of the basic frame structure. Movement of the housing isguided and stabilized against rocking by four guide bars 29 which slideagainst the cross plates 27. The guide bars are secured to plate 25 andextend vertically therethrough.

Communicating with the conduit interior of frame 19 is fluid conductor28. The conductor is connected to a valve and a means for supplying avacuum to the interior of the conduit. The valve and vacuum means, beingconventional, are not shown. The bottom edge portions 44 of frame 19 areprovided with passageways 46. These passageways may take the form ofslots, orifices or the like and are arranged to contact and retain byvacuum an upper film placed adjacent thereto either manually or by anupper sheet transportation assembly such that shown generally byreference numeral 16.

The upper sheet transportation assembly 16 comprises a carriage framewhich is adapted for supporting a top film and moving it from a firstposition shown in phantom in FIG. 4 to a second position beneath housing18, also shown in FIG. 4. To accomplish such movement the carriage frameincludes a rectangularshaped vacuum frame 52 formed from a continuoushollow conduit and a set of spaced apart matching rollers. The topsurface of the conduit contains fluid ducts 54 in the same manner asframe 19 and may conveniently be a mirror image of the bottom portion 44of housing frame 19. The purpose of having the vacuum frame 52correspond in shape to the housing frame 19 is to facilitate thetransfer of a top film from the vacuum frame when its positioned beneaththe housing frame. The interior of the conduit of vacuum frame 19 is incommunication with fluid conductor 55 which, in turn, is connected to avacuum source (not shown). A top film is held to the top surfaces ofvacuum frame 52 by excavating air from ducts 54 through the vacuum frameconduit 52 and conductor 55. The film is situated on the vacuum frame ina manner to overlap the ducts such that a pressure differential will becreated and atmospheric pressure will push the film against the regionsof lower pressure about the ducts beneath the film.

It is to be understood that single precut top films may be manuallypositioned adjacent the bottom 44 of frame housing 19 or manually placedupon the vacuum frame and transported into the vacuum sealing sectionor, as shown ,in FIG. 4, predetermined lengths of film shown as 61 inFIG. 4 may be pulled into the sealing section from supply roll 60. Toaccomplish the latter alternative, the supply roll rests by gravity onidler rollers 62 so that when the carriage frame moves into the vacuumsealing section, the roll will freely rotate and allow the requisiteamount of film to be withdrawn. A vacuum of 15 inches of mercury or moreat ducts 54 creates sufficient pressure differential across the top film61 to overcome any frictional resistance to the rotation of the supplyroll and prevent the film from slipping off the vacuum frame. It isdesirable to have the ducts, slots, orifices or the like located about amajor portion of the top surface of the vacuum frame periphery so as touniformly hold the top film and prevent creasing or wrinkles.

In some instances, such as when a full heavy supply roll is being used,it has been found desirable to use supplementary retention means 58.This may take the form of a pair of pneumatic or hydraulic operatedplungers 48 mounted on frame 50. The plungers reciprocate up and down asshown by arrow B in FIG. 4. In the down position the plungers contactthe film 61 and press it against the top surface of the vacuum frame.Additionally, it may be desirable to provide the vacuum frame with acenter plate, shown as 57 in FIG. 5. This is to provide a flat supportarea for the film and prevent it from sagging at its midpoint. The platewill also facilitate the positioning of single precut films over theframe when such are used.

To provide for movement of the carriage frame, a lower offset portion 59is utilized in conjunction with a roller assembly shown generally byreference numberal 63 in FIG. 5. In the embodiment shown, the rollerassembly includes two pairs of spaced-apart upper rol- Iers 66,67mounted for rotation above frame portion 59 and on opposite sidesthereof. Two pairs of spacedapart lower rollers 68,69 are mountedbeneath frame portion 59. Each of the lower rollers are positioneddirectly beneath a corresponding upper roller and -are spaced therefroma distance sufficient to engage a pair of opposing tracks 70 which areaffixed to the top edge portion of support angles 71. Preferably, tracks70 are in the shape of a rod and the upper rollers 66,67 presem aconcave circumferential surface. In this manner, the frame will beeffectively guided and maintained in position during its traverse to andfrom the aforementioned first and second positions. Note also thatrollers 68,69 engage the underside of angles 71 thereby preventingforward tipping of the carriage frame.

Movement of the carriage frame along the track is accomplished bycarriage drive means 72. As shown in FIG. 4, this includes a cylinder 75which pneumatically or hydraulically moves an internal rod and pistonassembly (not shown) which is connected to drive chain or wire 73.Attached to the wire is connector 74 which is also secured to the bottomof the carriage frame. In this way hydraulic or pneumatic force fromdrive means 72 is transmitted through the wire 73 and connector 74 toframe 50 thereby causing the movement thereof along track 70. Mechanicaleccentric means, electric drive means or various combinations of eachcould also be used for the drive means of the present invention.

An advantage of the above-described system is that it is substantiallytrouble-free and can very easily be adjusted for different strokelengths. For example, differ ent sized products will require differentlengths and/or widths of top film to be pulled into the sealing section92. As such, it is a simple matter to adjust either the distance thewire 73 and connector 74 move or the position of the connector on thewire.

When carriage frame 50 is in the second position, a film cuttingmechanism shown generally as 78 in FIG. 6 is activated to sever thefilm. The severing occurs only after the film has been released fromvacuum frame 52 and retained on the lower edge portions 44 of housingframe 19 and the vacuum frame retracted back to its first position. thecutting means 78 may be a hot cutting wire shown as 79 in the preferredembodiment or rotary cutters or conventional knife means known in theart.

When the carriage frame has been retracted to its first position, thecutting mechanism'is actuated causing fluid to enter cylinders '84 andeffect the downward movement of shafts 84. Opposite ends of resistancewire 79 are secured to shafts by ceramic connectors 83. The lowermostposition of the cutting wire 79 after it has passed through film 61 isshown in phantom in FIG. 6.

After the film 61 has been severed, housing 18 will reciprocate to alower position to sealingly engage the vacuum plate 14. In a preferredembodiment of the present invention, the housing 18 is provided with theaforementioned heating means 80. The heating devices are convenientlymounted on shield 21 so that the upper film will become more efficientlysoftened by both reflection and convection currents.

As illustrated in FIG. 15, an essential feature of the present inventionis the position of the top film 61 and housing frame 19 relative tofluid passageways 32 and the side edges of bottom film 38. Thepassageways 32 are in communication with fluid conduits 34 which areconnected to a vacuum source (not shown). It is important that thepassageways 32 remain unobstructed during the sealing process so thatthe evacuation of air may be as complete as possible from the package.In part, this can be accomplished by locating the passageways proximatethe side edges of the bottom film and preferably beyond the peripherythereof shown in FIGS.s l4 and 15. Alternatively, shields shown as 42 inFIGS. 11a and 1 117 may be used to maintain the passageways open whenwide bottom films are used or to prevent in advertent misplacement ormisalignment of the bottom film from obstructing the passageways.

The passageways 32 are shown as slots in the drawings but couldjust wellbe a series of orifices or other type of duct. The passageways should belocated substantially parallel to the side edges of the bottom film toproduce the most effective air evacuation from the region between thepackaging media. It is essential that there should be at least onepassageway on the vacuum plate, but preferably two should be usedadjacent each opposite side edge of the bottom film to effect a balancedevacuation of air. This is advantageous because it provides a quickerand more thorough removal of air. It also facilitates a more balancedvacuum draw of the top film over the item to be packaged and it producesa more uniform wrinkle-free bond between the films at their interfaceabout the periphery of the item.

It is to be understood that the vacuum plate 14 can be removed andexchanged for a plate having passageways and/or templates or the likelocated in different positions to accommodate various types and sizes ofproducts. Of course, the configuration of housing frame 19 couldlikewise be changed to accommodate the different products and conform tothe changed vac uum plate. It is important, however, that the bottomedges 44 encompass the fluid passageways 32 to form an effective sealagainst the vacuum plate in a manner to be hereinafter described.

As advantageous aspect of the present invention resides in the use of anintegral continuous bottom film conveying system operable with a unitarydrive means. In general, the system comprises a drive means, showngenerally 22 in FIG. 8, the previously described first and secondsupport sections, a drive roller 104, and a pair of friction wheels 96.The wheels operate to frictionally engage the flattened side portions ofthe completed package at the nip between the wheels and drive roller.Since the bottom film is continuous, fresh film will be drawn from astorage roll or from the embossing assembly through the apparatus is anamount equal to the distance each successive package is moved. Theamount of rotation is predetermined so that the appropriate amount offilm will be drawn into the sealing section to adequately cover theproduct being packaged. It is to be noted that due to the inherentresilience of the packaging films, a package will be pushed downstreamfrom the friction rollers as it passes therethrough into the cutting andunloading zone.

To provide the necessary pressure adjustment on the wheels 96 foreffectively frictionally engaging the package periphery, the frictionwheels are mounted on pivot arms 98. Downward pressure of the frictionwheels against drive roller 104 is effected by adjustment of threadedbolts 106. As the bolts are screwed down against housing plates 107,their offset position on arms 98 causes the arms and wheels to rotatecounterclockwise against the drive roller. It is to be understood thatopposing clamp means reciprocating on a track would work equally as wellas a means for moving the bottom film and packages through the system.

In the preferred embodiment the drive means 22 of the bottom filmconveying system includes pneumatic cylinder 116 having a rod 120pneumatically reciprocated therein. Attached to the top of the rod isbracket 1 I8 which is secured to connector plate 124. The plate linkstogether the ends of primary drive chain 122. The drive chain engagesthe teeth of idler sprocket 130 and drive roller socket 132. The driveroller socket is equipped with a conventional ratchet mechanism suchthat the drive roll 104 will be power driven only in the direction shownby arrow C in FIG. 9.

Located on the opposite end of drive roll I04, sprocket I35 transmitsthe rotational force thereof, through chain I21 to the auxiliary rollers97u,b,c. (See FIGS. 2 and I3). Roller 970 is equipped with a doublesprocket I40 so that the rotational force of roll 104 will be furthertransmitted by chain I23 to a sprocket 139 on the end of secondary driveroller 134. As previously described, the secondary drive roller I34functions to rotate belt 130 of the first support section.

It can be seen that the above drive system provides a highlyadvantageous unitary means for not only moving a bottom film and packagethrough the packaging apparatus, but it also drives the cooperatingsupplemental conveying means embodied in the two support sections. Thedrive system also imparts a high degree of versatility to the conveyingsystem of the present invention in that different sized sprockets may beused to effect variable ratios of rotation to slow down or speed up therollers and/or belt. Of course, the system can be operatedintermittently without the conveying system to individually packageitems.

Referring now to the package severing means 112 (see FIGS 1, 9 andlocated immediately downstream from the friction wheels, the use of amovable hot wire system is shown. This system consists of a thinresistance wire 142 connected at opposite ends to a eeramie adaptor 141which is mounted on bracket 144. The bracket is provided with a rollerassembly adapted to engage and roll against a side portion of supporthousing 15 adjacent slot 146. A pair of guide rollers 152 are mounted onthe lower inner face of the bracket and are positioned to slide alongthe inner edges 153 of slot 146. A transverse support roller I54 Slidesalong the outside sidewalls of housing 15 adjacent the slot 146. Bracket144 is secured to cross plate 156 which is reciprocated up and down bylift devices 158. When a package formed from the continuous bottom film38 reaches the unloading zone 160 (see package M in FIG. 13), the liftdevices are actuated to move the hot wire through the film.

Continuing on the optional bottom sheet-forming assembly shown generallyby referene numeral 12 in FIGS. 1 and 2 and schematically in FIG. 12, asupply roll 201 is shown having a plain flat film drawn therefrom over aportion of vacuum drum 206 and across tension roller 205 into theapparatus shown by arrow D. The drum surfaces are provided with a seriesof orifices 204 such that after the film has been heated, either byinternal means within the drum or by auxilliary heating means 208, thefilm becomes pliant and can be partially drawn into the orifices on theface of the drum. Upon cooling, the film will have a series ofprojections spaced throughout its surface. The optional heating sectionof the drum is shown by reference numeral 210 and the vacuum section isshown by numeral 212.

Alternatively, it is within the purview of the present invention toutilize a mechanical device for creating a series of projections on thebottom film. This may be accomplished by passing a film through the nipofa pair of rollers 214, 2l6one of which has outwardly extendingprojections 218 that engage matching recesses 220 on the opposingroller. The film may be optionally heated by heated rollers or externalmeans as it passes through the forming device.

The advantage of the mechanical device is that it is simpler andpresents no problem of the film becoming overheated due to thesequential operation of the apparatus.

As previously mentioned, it may be convenient to have the projectionsformed in the bottom film in a separate operation and stored in rolls.In such case, the embossed film would simply be substituted for roll 201and fed directly into the apparatus.

To obtain a better understanding of the method of the present inventionreference should be made to FIGS. 13, I4 and 15. In FIG. I3 productsbeing packaged in a sequential manner on a continuous bottom film areshown schematically by letters M, N, O, and P. To begin operation, thebottom film with its projections directed upwardly is pulled throughboth the first and second support sections and the sealing section, andinserted between the nip of wheels 96 and drive roller 104. Similarly,an upper film is placed over the vacuum frame 52. The vacuum source isopened such that when the machine is activated, a predetermined sequenceof events will occur.

With the vacuum source in communication with conduit 55which is openedby conventional valve means (not shown). air will be removed'from thevicinity of ducts 54. The resultant pressure differential will functionto retain the top plastic film about the perimeter of the vacuum frame.Additionally, the supplementary retention plungers 48 may be activatedto press the film against the vacuum frame to further prevent the filmfrom being twisted or slipping off the frame. An electronic controlmeans activates carriage drive means 72 to move the carriage assemblyfrom the first position shown in phantom in FIG. 4 to the secondposition beneath the housing 18. At this point the hold-down plungers 48are released and the vacuum to the frame 52 is shut-off. Simultaneouslya vacuum source is placed in communication with fluid conduit 28 andhousing frame 19. Air is evacuated through orifices 46 and about thebottom edge portion 44 such that the top film will be released from thevacuum frame 52 and become pushed by pressure differential against thebottorn edges 44 of the housing frame. Note that the second position ofthe carriage assembly facilitates this in that it extends to a locationsubstantially directly beneath the housing and in close proximity to thelower edges 44.

After the housing has received the top film 61, the carriage drive means72 operates to return the carriage frame to its first position.Immediately after this has occured. top film severing means 78 isactivated to move a hot wire through the film and sever it completely.The housing is now ready to move to a lower position upon thevacuum-sealing plate 14. Of course the above sequence could beeliminated by simply manually placing a precut sheet of film into placeagainst the edges 44. Such may be more convenient when packagingseparate or unusual items rather than a large number of similar articleswhere speed and high volume are not the criteria.

About the time the severing means 78 is operated heaters 80 areactivated so that the upper film is being warmed into a pliant orformable state. This occurs a result of the heating action of theheating means located within the housing and beneath shield 21.Depending upon the type of heaters being used, it may be preferable toleave them on continuously.

Before the housing descends to a lower position, a vacuum source isplaced into communication with conduits 34 and passageways 32. At thispoint it will be recalled that the dimpled film has been stretchedacross the vacuum sealing plate 14 and is located between thepassageways 32 as shown in FIGS. 14 and 15. Note that an article ofmanufacture, a meat product, a foodstuff, or some other type of productdesignated has been placed upon the embossed bottom film. Thispreferably occurs at the first support means located which has now beensequenced into the vacuum sealing section.

As the housing [8 descends over the product, the top film being in asoftened state and secured about its periphcry by vacuum, stretches overthe product while the housing continues its downward movement.Simultaneously. air is being evacuated from the edges of the embossedbottom film. As the top film continues to be lowered air is removed fromthe area shown as 90 in FIG. 14. This is defined as the region below theupper film and within the perimeter of the area of sealing engagementbetween frame portion 44 and the vacuum plate. With the presentinvention. evacuation of air continues even after the top film has madeinitial contact with the top surfaces of the projections of the bottomfilm. This occurs through the interstices between the projections asshown by the arrows in FIGS. 14 and 15.

After substantially all the air is removed, it is believed that thesomewhat resilient projections become collapsed due to the pressuredifferential between the atmosphere and the reduced pressure between thefilms. At this point the top film Commences to bond with the bottom filmat the annular area of their overlap about the product periphery.Alternatively, depending on the type of product being packaged, it maybe desirable to heat the bottom sealing plate to enhance the seal.However, this is entirely optional and not necessary or even desirablein some cases.

After the top film has been tightly stretched over the product andsealed about the product periphery, the vacuum source is shut-off toboth the vacuum plate and housing 18. The housing reciprocates back toits upper position and drive means 22 is actuated to transport thepackage from the vacuum sealing section to the second support section.It is contemplated that the sealing process is taking place, an operatorwill be placing another product, shown as P in FIG. 15, upon the bottomfilm at the first support section. Therefore, it can be seen thatproduct P will be drawn into the sealing section product 0 is pulled tothe second support section.

As successive products are placed onto the bottom film, a continuouschain will be formed until the bottom film is severed. Since the:sealing process requires a certain period of time, newly formedpackages will have a brief dwell period, corresponding to the sealingtime, in which the films may cool. The package will then be alternatelypulled and then pushed between wheels 96 and roller 104 to an unloadingarea denoted by reference numeral 160. At this point the package shown Mwill be severed from the continuous bottom film by severing means 112and removed for final stacking, storage and/or shipment.

Note that with the present invention there is no airtight chamberrequired above the upper film 61. A seal is formed about the peripheryof the housing 18 at edges 44 the housing engages the upper film andpresses it against the surface of the vacuum sealing plate 14. Toenhance this seal a resilient gasket shown at 92 in FIG. 15 may beprovided on the vacuum plate to engage frame portion 44. When thehousing engages the bottom film radially outward from passageways 32 andpresses it against the vacuum plate or gasket (and transverse portionsof the bottom film if such is continuous), all air contained withinregion will be evacuated. When the pressure differential is great enoughto overcome the inherent resilience of the upwardly extendingprojections and cause: their collapse and/or cause the upper film toflatten against the bottom film, an airtight seal will be formed.Because of the seal delaying action caused by the projections, theinterstitial air evacuation passageways formed thereby, and the factthat air is being removed from opposite sides of the package, it can beseen how the present invention produces a tightly sealed package withsubstantially all air removed.

Of course, the type of film, its resilience andability to stretch areimportant. The films are preferably of a thermoplastic material such as'Surlyn or various thermoplastic coated laminates such as polyethylene,cellulose acetate, polyethylene-regenerated cellulose, regeneratedcellulose films, rubber hydrochloride films,

polyvinyl films or metallic laminated foil films having a thermoplasticcoating. Plastic or adhesive-coated embossed members whether they arerigid or semi-rigid, could be substituted for the bottom film. Note thatwith the present invention substantially any configuration orarrangement of projections may be utilized on the bottom packagingmaterial. Hemispherical protuberances are shown as uniformly spacedabout the surface of the bottom film in the drawings of the preferredembodiment. However, the projections may take the shape of pyramidalprotuberances, straight or zigzag ridges, or any other design providinga number of intersticies between which air may be drawn.

it should be noted that the closer together the projections, the lesssusceptible they are to flattening by the pressure differential duringevacuation and sealing. Similarly, the more resilient and/or the closertogether the projections, the more thorough will be the excavation ofair about the product. However, the material or projections should notbe too rigid to prevent a final seal to occur with the top film. Ofcourse, due to the preferred softening of the upper film, this would bean uncommon occurrence. in this regard, reference is made to thedisclosure of US. Pat. No. 2,778,171

which discloses the use of various types of film projections andpackaging materials to facilitate the evacuation of air from a pouch. Tothe extent of utilizing various types of projections and packagingmaterials, this patent is hereby incorporated by reference.

The present invention is particularly suitable to the packaging of foodproducts wherein packaging materials having a relatively low air oroxygen permeability should be utilized. in this regard, substantiallyimpermeable films may be coated with heat activatable adhesives andutilized. Examples of such would be the use of a polyethylene film witha coating of ethylene vinyl acetate. Such a film when heated will allowthe tight bonding and sealing of upper films to lower films. Of course,a film must be chosen that will stretch and draw down over the shape ofthe product being packaged without being disproportionately stretched,weakened or torn.

As mentioned previously, the present apparatus operates sequentiallywith the dwell period between movements being conveniently dictated bythe time required to seal the product at the vacuum sealing section.This may be automatically controlled by timer means and electricalcircuitry which coordinates the activation of the carriage framemovement and the housing means movement together with the vacuum conduitopenings and closings.

Although pneumatic or hydraulic means have been shown to drive thecarriage frame, housing and support means, electric motors, cammechanisms or the like, operated by solenoid devices would work equallywell. Likewise, a central vacuum source may be utilized in conjunctionwith the sequential operation of valves in the various fluid conduitsconnecting the various outlets at the appropriate time.

While the invention has been described with respect to a specificembodiment, it will be apparent to those skilled'in the art that variousmodifications and improvements may be made without departing from thescope and spirit of the invention. Accordingly, it is to be understoodthat the invention is not to be limited by the specific illustrativeembodiments, but only by the scope of the appended claims.

I claim:

1. in an apparatus for packaging articles between an upper and lowersheet comprising;

vacuum forming means;

a vacuum base member supported by a frame, said base member includingpassageways in communication with said vacuum forming means, saidpassageways being open at predetermined locations on said memberproximate peripheral portions of a lower sheet placed thereon;

a lower sheet conveying system comprising drive means engagable withsaid lower sheet at a point downstream from said vacuum base member, andsheet support members located along the path of travel of said lowersheet adjacent said vacuum base member; and,

a movable housing mounted above said base member on said frame includingmeans to reciprocate said housing between an upper position and lowerposition, and including heating means and upper sheet retaining meansoperating in response to the position of the housing, said housing beingadapted to substantially sealingly engage said base member radiallyoutward from said passageways.

2. The apparatus of claim 1 including sheet cutting means locateddownstream from said drive means to sever individual packages from saidlower sheet.

3. The apparatus of claim 1 including an upper sheet transportationassembly adjacent said housing assembly including a carriage means forcarrying the upper sheet of packaging material from a first position toa second position beneath said housing when said housing is in the upperposition, retention means on said carriage means for releasablyretaining said upper sheet on said carriage means, and means for movingsaid car riage means from said first position to said second posi tion.

4. The apparatus of claim 3 wherein said upper sheet retaining means andthe carriage retention means comprise vacuum ducts in communication withthe vacuum forming means and located about the sheetcontacting portionsof said housing and carriage means.

5. The apparatus of claim 3 wherein said upper sheet is initially in acontinuous roll, including sheet cutting means located between saidcarriage means and said housing and activated to cut individual sheetsfrom the continuous roll when said carriage means is in the secondposition.

6. the apparatus of claim 5 wherein said upper sheet transportationassembly includes secondary retention means mounted on said carriagemeans for securing said upper sheet against slippage during movementfrom said first position to said second position.

7. The apparatus of claim 1 including control means comprising:

means to activate said upper sheet retaining means for retaining theupper sheet on said housing;

means to activate the movement of said housing from said upper positionto said lower position; and,

means for activating said heating means at least during the period saidhousing moves from said upper position to said lower position.

8. The apparatus of claim 3 including control means comprising:

means to cause said upper sheet retaining means to retain the uppersheet upon said housing;

13 14 means for activating said heating means at least durmoved to saidfirst position; and,

8 the Period Said housing move-S from Said pp said control means furtherincluding means to conposition to fi l position; trol the time saidhousing is in said lower position means for activating the movement ofsaid carriage means between said first and second positions; and meansto aqnvate Swd dnve means when Sald means to activate the movement ofsaid housing to housing moves said pp Positionsaid lower position aftersaid carriage means has

1. In an apparatus for packaging articles between an upper and lowersheet comprising; vacuum forming means; a vacuum base member supportedby a frame, said base member including passageways in communication withsaid vacuum forming means, said passageways being open at predeterminedlocations on said member proximate peripheral portions of a lower sheetplaced thereon; a lower sheet conveying system comprising drive meansengagable with said lower sheet at a point downstream from said vacuumbase member, and sheet support members located along the path of travelof said lower sheet adjacent said vacuum base member; and, a movablehousing mounted above said base member on said frame including means toreciprocate said housing between an upper position and lower position,and including heating means and upper sheet retaining means operating inresponse to the position of the housing, said housing being adapted tosubstantially sealingly engage said base member radially outward fromsaid passageways.
 2. The apparatus of claim 1 including sheet cuttingmeans located downstream from said drive means to sever individualpackages from said lower sheet.
 3. The apparatus of claim 1 including anupper sheet transportation assembly adjacent said housing assemblyincluding a carriage means for carrying the upper sheet of packagingmaterial from a first position to a second position beneath said housingwhen said housing is in the upper position, retention means on saidcarriage means for releasably retaining said upper sheet on saidcarriage means, and mEans for moving said carriage means from said firstposition to said second position.
 4. The apparatus of claim 3 whereinsaid upper sheet retaining means and the carriage retention meanscomprise vacuum ducts in communication with the vacuum forming means andlocated about the sheet-contacting portions of said housing and carriagemeans.
 5. The apparatus of claim 3 wherein said upper sheet is initiallyin a continuous roll, including sheet cutting means located between saidcarriage means and said housing and activated to cut individual sheetsfrom the continuous roll when said carriage means is in the secondposition.
 6. the apparatus of claim 5 wherein said upper sheettransportation assembly includes secondary retention means mounted onsaid carriage means for securing said upper sheet against slippageduring movement from said first position to said second position.
 7. Theapparatus of claim 1 including control means comprising: means toactivate said upper sheet retaining means for retaining the upper sheeton said housing; means to activate the movement of said housing fromsaid upper position to said lower position; and, means for activatingsaid heating means at least during the period said housing moves fromsaid upper position to said lower position.
 8. The apparatus of claim 3including control means comprising: means to cause said upper sheetretaining means to retain the upper sheet upon said housing; means foractivating said heating means at least during the period said housingmoves from said upper position to said lower position; means foractivating the movement of said carriage means between said first andsecond positions; means to activate the movement of said housing to saidlower position after said carriage means has moved to said firstposition; and, said control means further including means to control thetime said housing is in said lower position and means to activate saiddrive means when said housing moves to said upper position.